This invention relates to a composition comprising thermoplastic polymer, such as polypropylene, and fluoroaliphatic radical-containing surface-modifying additive which modifies a surface property of the composition, such as water repellency. In another aspect it relates to shaped articles, such as fibers, comprising said composition, and methods of making said articles.
Thermoplastic polymers are widely used to make a variety of shaped articles including, for example, fibers, blown films, cast films, extruded sheets, and foams. Fibers, films, or other shaped articles are often prepared by melt extrusion. In many cases it is desirable for the shaped article to have low surface-energy, oil- and water repellency, or anti-soiling properties. In other cases it is desirable for the surfaces of the shaped article to be hydrophilic. Various fluorochemical compositions have been used to impart desired surface-properties to polymers and to the surfaces of shaped articles made therefrom.
Fluorochemical compositions have also been used as processing aids in the extrusion of synthetic resins into fibers and films as described in Rudkin et al., xe2x80x9cFluorocarbon Elastomer Aids Polyolefin Extrusion,xe2x80x9d Plastics Engineering, March 1986, pp 83-861 and in U.S. Pat. No. 4,855,360 (Duchesne et al.)
Topical addition of fluorochemical additives has been used to impart desired surface-properties, for example, water repellency or hydrophilicity. See, for example, Banks, Ed., Organofluorine Chemicals and Their Industrial Applications, Elis Horwood Ltd., Chichester, England, 1979, pp 215-234.
Fluorochemical additives have also been incorporated into compositions by melt extrusion of a blend of synthetic fiber-forming polymer and fluorochemical additive. For the purpose of the specification, such additives will be referred to as xe2x80x9cmelt additivesxe2x80x9d. Such melt extrusion is described, for example, in F. Mares et al., xe2x80x9cModification Extrusion Techniques,xe2x80x9d Textile Research Journal, Vol. 48, No. 4, pp. 218-229, International Application No. PCT/US90/05928 (Sterling et al.), and U.S. Pat. No. 3,899,563 (Oxenrider et al.). Compositions may be incorporated into polymer melts by injection of the composition into the molten polymer stream immediately on exiting the extruder barrel according to the procedure described in U.S. Pat. No. 4,933,229 (Insley et al.).
U.S. Pat. No. 5,025,052 (Crater et al.) describes certain fluoroaliphatic-containing oxazolidinones useful as melt additives in thermoplastic polymers. Fibers, films, and other shaped articles can be prepared by melt extrusion or injection molding of a composition comprising a thermoplastic polymer and said oxazolidinone. The oxazolidinone imparts low surface energy to the surfaces of the resulting fibers, films, and other shaped articles.
U.S. Pat. No. 5,043,195 (Skrivseth) discloses flexible sheet material comprising an antistatic layer. Said antistatic layer comprises a polymer having dispersed therein a fluoroaliphatic sulfonamido polyether.
The properties of thermoplastic polymers have also been modified by blending with other polymers. For example, U.S. Pat. No. 4,759,984 (Hwo) discloses compositions comprising polybutylene, polypropylene, and modified ethylene vinyl acetate (EVA). Said blends are said to produce a peelable heat seal between substrates on which it is carried. European Patent Application No. 337,662 (Ferrar) discloses a polymer blend comprising polypropylene and PB 0200 polybutylene, wherein the polybutylene is said to enhance the tenacity of the oriented polymer. See also, M. Sanders, xe2x80x9cUse of Polybutene to Improve Impact Properties of Polypropylene Film,xe2x80x9d NTEC 190, P. 1167.
Briefly, in one aspect, this invention provides thermoplastic compositions comprising a major amount of a first thermoplastic semi-crystalline polymer, such as polyolefin (e.g., polypropylene), a fluoroaliphatic radical-containing surface-modifying additive (e.g., an oxazolidinone), and a minor amount of a second thermoplastic polymer (e.g., polybutylene) which decreases the percent crystallinity of the first thermoplastic polymer and which increases, or enhances, the effect of the surface-modifying additive. The surface-modifying additive is present in an amount sufficient to impart desired properties to the surfaces of shaped articles of the composition. Said second polymer is present in an amount sufficient to increase the effect of said surface-modifying additive, i.e., an equal surface-modification may be obtained with less additive, or a greater surface modification may be obtained with an equivalent amount of additive. Said first polymer and said second polymer can each be a single polymer or a mixture of polymers.
In another aspect, this invention provides shaped articles comprising the composition of this invention. Said surface-modifying additive is dispersed within the shaped article and is present at the surfaces of the shaped article.
In a further aspect, this invention provides methods of preparation of shaped articles with modified surface properties.
As used herein, xe2x80x9cmajorxe2x80x9d and xe2x80x9cminorxe2x80x9d amounts means that there is more of the major amount than of the minor amount. As used herein, xe2x80x9cpolymerxe2x80x9d means a polymer or a mixture of polymers. For example, said first polymer can be polypropylene or a mixture of several polypropylenes. The compositions of this invention, which comprise a three-component blend of first polymer, second polymer and surface-modifying additive, have enhanced surface-modification, for example, increased water repellency or hydrophllicity, compared to two-component blends of thermoplastic polymer and surface-modifying additive, or two-component blends of first and second polymer.